Hydraulic implement control for tractors



May 11, 1965 Filed Dec. 5, 1962 R. CARLIN ETAL HYDRAULIC IMPLEMENT CONTROL FOR TRACTORS 2 Sheets-Sheet 1 A x/kkormag R. CARLIN ETAL HYDRAULIC IMPLEMENT CONTROL FOR TRACTORS May 11, 1965 2 Sheets-Sheet 2 Filed Dec. 5, 1962 position.

United States Patent 3,132,729 7 HYDRAULIC LEMENT CONTROL Fen TRACTORS Robert Carlin and John R. Plate, Milwaukee, Wis, as-

signors to Allis-Chalmers Manufacturing Company, Milwaukee, Wis.

Filed Dec. 5, 1962, Ser. No. 242,390 4 Claims. (Cl. 172-7) The invention relates to hydraulic power lift systems for tractors, and it is concerned more particularly with a combined power lift and automatic weight transfer systern.

Raising and lowering of tractor drawn equipment, such as a plow, and automatic transfer of weight from such equipment to the tractor drive wheels when needed for increased traction may be accomplished, according to well known principles, by means of a hydraulic system including a manually adjustable hydraulic control valve and a device for sensing variations of the draft which is transmitted from the tractor to the drawn equipment. The system preferably includes a supply of operating fluid which is pressurized by the power of the tractor motor.

desired lowering of the equipment from its raised position.

For practical reasons such leakage cannot be entirely avoided; and if the equipment is to be maintained in raised position for some length of time, the fluid motor must be supplied with make-up oil to replace the leakage loss.

In. order to supply make-up oil it has heretofore been customary to adjust the manually operable control valve temporarily at intervals from its hold position to its lift This practice requires additional operator attention and for that reason is unsatisfactory, particularly when an implement is to be kept at its fully raised position for a relatively long time, as during transport from one place of work to another.

Generally, it is an object of the invention to provide an improved hydraulic power lift system wherein a fluid motor, such as a one-way lifting ram, is automatically sup plied with make-up oil.

More specifically, it is an object of the invention, to

provide an improved hydraulic power lift system of the above mentioned character wherein make-up oil is auto matically supplied to a lifting ram as soon as the ram is extended to a predetermined implement lift condition.

A further object of the invention is to provide an improved hydraulic power lift system of the above mentioned character which also serves to transfer weight from the implement to the tractor drive wheels as needed for increased traction. I

A still further object of the invention isto provide an improved hydraulic power lift and weight transfer system'wherein make-up oil for the fluid motor is derived from the same source of pressure fluid which furnishes power for transferring weight from the implement to the tractor.

A still further object of the invention is to provide an improved combined power lift and weight transfer system of the hereinabove mentioned character which is simple in construction, eificient in operation and which lends itself to manufacture at relatively low costs.

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' Referring to the accompanying drawings:

FIG. 1 is a diagrammatic view of a hydraulic power lift and weight transfer system incorporating the invention, a manually adjustable control valve of the system being shown in an implement hold position;

FIG. 2 is a detail view showing the manually adjustable control valve of FIG. 1 in an implement lift position;

FIG. 3 is another detail view showing the manually adjustable control valve of FIG. 1 in a weight transfer position; and

FIG. 4 is another detail view showing the manually adjustable control valve of FIG. 1 in an implement lowering position.

The implement lift and weight transfer system which is diagrammatically outlined in FIG. 1 comprises, in general: a first fluid pump 1, a second fluid pump 2, a power lift mechanism 3, a draft sensing device 4, a bypass valve 6 for the pump 2, an operating connection 7 between the power lift mechanism 3 and the valve 6, a sump 8, and a spool type directional hydraulic valve 9.

The pumps 1 and 2 have large and small output capaci- .ties, respectively, the pump 1, being preferably a multiple plunger pump of conventional construction, and the pump 2, while shown as a gear pump, may also be a plunger pump, preferably a single plunger pump, of conventional construction. Both pumps are connected in fluid receiving 'relation with the sump 8, the pump 1 being connected at its suction side with a sump 10, and the pump 2 being connected at its suction side with a sump line 11. Driving power for the pumps is derived from a tractor motor, not shown, in conventional manner; that is, the pumps will be running as long as the tractor motor is running.

A rear part of the tractor on which the pumps 1 and 2 and other components of the system are installed is shown in dash-dotted lines in FIG. 1 and generally designated by the reference character 12.

The power lift mechanism 3 comprises a conventional implement lift arm 13 which is pivotally mounted at 14 on the tractor body and which has a depending actuating arm 16. A hydraulic ram has a plunger 17 which is pivotally connected at 18 with the actuating arm 16, and the cylinder 19 of the ram is pivoted at 21 on the tractor body.

. The lift arm 13 has a depending link connection 22 with the draft tongue 23 of an implement, such as a plow,

'not shown. The draft tongue 23 is hitched to the tractor body in conventional manner through the draft sensing device 4- which comprises a coupling arm 24, pull rod 25, load sensing spring 26, rocker 27 on valve 6 and link 28 connecting the lower end of rocker 27 with the forward end of rod 25. Ann 24 is pivoted at 29 on the tractor body and has a hook connection with an eye at the for ward end of the draft tongue 23, which may be constructed as shown more fully in US. Patent 2,834,277, issued on May 13, 1958, to W. H. Tanke for Quick Hitch System. The load sensing spring 26 bears at its rear end upon an abutment on the tractor body, and at its forward end against a collar 31 on the rod 26 which extends through the spring and is pivotally conected at its rear end with the coupling arm 24. In operation, when draft is transmitted from the tractor to an implement through the draft input passage 32 which communicates with the fluid de- -mechanism 3 and the valve 6 comprises a lever 41 which is pivoted intermediate its ends at 42 on the casing of the valve 6. The lower end of the lever 41 is disposed side by side with the upper end of the rocker 27 in abuttable relation to the head 39 of the valve control element 37. The adjacent ends of the rocker 27 and lever 41 are freely movable relative to each other so that the rocker 27 and the lever 41 may be actuated independently of each other to move the valve control element 37 into its closed position, as will be discussed more fully hereinbelow. The upper end of the lever 41 has a lost motion connection with a cable 43 which is anchored at one end onthe actuating arm 16 of the power lift mechanism and which has a stop 44 secured to its other end. The cable 43 extends slidably through an eye 46 at the upper end of the lever 41. In the condition of the mechanism as shown in FIG. 1, the valve 6 is open, and the stop 44 is spaced from the eye 46 so that the valve will remain open when the lift arm 13 swings from its full line position to the dash-dotted line position indicated by the reference character 47. However, movement of the lift arm 13 to the position indicated by line 47 brings the stop 44 into engagement with the eye 46, and the valve 6 will be closed by continued upward movement of the lift arm 13 to its fully raised position which is indicated by the dash-dotted line 48.

The pivoted actuating lever 41 and its lost motion connection with the rockable implement lift structure 13, 14, 16 by means of the cable 43 represent motion transmitting means operatively interposed between the driven element of a fluid motor 17, 19 and the bypass valve 6 so as to close and open the bypass valve in response to movement of the driven motor element 17 in implement raising and lowering directions, respectively, beyond the predetermined position of adjustment corresponding to the dash-dotted line position 47. The dash-dotted line position 48 corresponds to the maximum implement lift position of the driven motor element 17, and the mentioned predetermined position of the driven motor element is closely adjacent to its maximum implement lift position.

The hydraulic control valve 9 which is diagrammatically shown in the upper part of FIG. 1 is an open center, four position, sixconnection, directional spool valve. It comprises a casing 49 which has a valve bore 51 and axially spaced radial enlargements thereof presenting, respectively, a first inlet chamber 52; a second inlet chamber 53; first and second exhaust chambers 54 and 56; a drain chamber 57 for seepage fluid; a delivery chamber 58; and first and second transfer chambers 59 and 61. The first inlet chamber 52 communicates with the fluid delivery side of the first fluid pump 1 through a connecting line 62; the second inlet chamber 53 communicates with the fluid delivery side of the pump 2, and with the input passage 32 of the bypass valve 6 through one branch 63 of an internal passage 64 of the valve housing 49 and through connecting lines 66 and 33; the first and second exhaust chambers 54 and 56 and the drain chamber 57 communicate with the sump 8 through exhaust lines 67, 68 and drain line 69, respectively, and the sump line the delivery chamber 58 communicates with the ram cylinder 19 through an internal passage 71 of the valve casing'49' and through a connecting line 72; and the first and second transfer chambers 59 and 61 are connected with each other through a U-shaped internal passage 73. The transfer chambers 59 and 61 further communicate with the first inlet chamber 52 terminates in the first inlet chamber 52. The junction of the U-shaped passage '73 with the passage 74 is controlled by a plunger type check valve 76 which is spring biased into the position shown in FIG. 1 so as to prevent return flow of fluid from the transfer chambers 59 and 61 into the first inlet chamber 52, and which yields to pressure created in the first inlet chamber 52 by the pump 1.

, A second branch 77 of the internal valve passage 64 communicates with the U-shaped passage .73 through bore 78 of a check valve plug '79 within the valve casing 49 and through radial bores 81 in the hollow plunger of the check valve 76. The check valve plug 79 contains a ball type check valve 82, and a coil spring 83 reacts between the ball of valve 82 and the plunger of valve 76. The ball of valve 82 is seated on an internal shoulder of the plug 79 so as to prevent return flow of fluid from the U-shaped passage 73 through the radial bores 81 into the bore 78 and branch 77 of the internal passage 64 of the valve casing 49.

Reciprocably mounted in the bore 51 of the valve casing 49 is a valve spool 84 which is selectively adjustable to any of the four positions in which it is shown in FIGS. 1, 2, 3 and 4, respectively. A manually operable lever 86 for effecting such adjustment of the valve spool is diagrammatically indicated in the drawings. As shown, the lever 86 is pivotally mounted on a stationary bracket 87 connected with the valve casing 49, and rocking of the lever 86 is transmitted to the valve spool 84 by a pin and slot connection 88.

The spool 84 of the valve 9 has a first land 89 which is operative to control fluid passage between the first inlet chamber 52 and the first exhaust chamber 54 as illustrated by FIGS. 1 and 2, and which is also operative to control fluid passage between the first transfer chamber 59 and the delivery chamber 58 as illustrated by FIGS. 3 and 4.

A second land 91 of the valve spool 84 is operative to control fluid passage between the second inlet chamber 53 and the second transfer chamber 61 as illustrated by FIGS. 2 and 3.

A third land 92 of the valve spool 84 is operative to control fluid passage between the second inlet chamber 53 and the second transfer chamber 61 as illustrated by FIGS. 3 and 4.

A fourth land 93 of the valve spool 84 is operative to control fluid passage between the delivery chamber 58 and the second exhaust chamber 56, as illustrated by FIGS. 3 and 4.

In the hold position of the valve 9 as shown in FIG. 1, the land 89 establishes communication between inlet chamber 52 and exhaust chamber 54, and between first transfer chamber 59 and delivery chamber 58. The land 91 disconnects second inlet chamber 53 from second transfer chamber 61. The land 92 is ineffective, and the land 93 disconnects the delivery chamber 58 from the second exhaust chamber 56. Pressure fluid is trapped in the ram cylinder 19 by lands 91, 8h, 93, and by check valves '76'and 82. The large capacity pump 1 idles, and the small capacity pump 2 could feed into the ram 3 through the ball check valve 821 if bypass valve 6 were closed. As explained hereinbefore, the valve 6 will be moved to its closed position by movement of the lifting arm 13 from a substantially raised position, as indicated by the dash-dotted line 47 to its fully raised position as indicated by the dash-dotted line 48.

Feeding of pressure fluid from the small pump 2 into the ram cylinder 19 while the lifting arm 13 is in its fully raised position will prevent gradual sagging of the lifting arm from its fully raised position due to leakage of pressure fluid, usually oil, from the ram cylinder 19 or due to seepage of pressure fluid out of the valve 9, as forinstance, past the land 93 into the second exhaust chamber 56, or past the plunger of check valve 76 into passage 74 and chambers 52;, 54. A relief valve 94 is associated with the bypass valve 6 as shown in FIG. 1 so that any oil supplied by pump 2 in excess of the make-up oil which is fed to the ram cylinder 19, may return to sump through outlet passage 34 of valve 6 and sump line 36.

In the lift position of valve 9 as shown in FIG. 2, the land 89 disconnects inlet chamber 52 from first exhaust chamber 54, and connects first transfer chamber 59 with delivery chamber 58. The land 91 disconnects second inlet chamber 53 from second transfer chamber 61; the land 92 is ineffective, and the land 93 disconnects delivery chamber 58 from second exhaust chamber 56. Pressure fluid from pump 1 passes through check valve 76, passage 73, first transfer chamber 59, delivery chamber 58, passage 71 and line '72 into the expansion chamber of ram cylinder 19. The small capacity pump 2 could feed into the ram cylinder through the ball check valve 82 but will do so only if draft of suflicient magnitude is transmitted through the sensing device 4 to close bypass valve 6. In that case both pumps 1 and 2 would feed pressure fluid jointly into the ram 3.

In the weight transfer position of valve 9 as shown in FIG. 3, the land 89 establishes communication between inlet chamber 52 and first exhaust chamber 54, and between first transfer chamber 59 and delivery chamber 58. The land 91 establishes communication between the second inlet chamber 53 and second transfer chamber 61. The land 92 is ineifective, and the land 93 disconnects delivery chamber 58 from second exhaust chamber 56. The large capacity pump 1 idles, consuming negligible power; and the small pump 2 likewise idles as long as the bypass valve 6 is open.

If an implement, such as a plow, is advanced in working position by the tractor and the valve 9 is in the weight transfer position, the sensing device 4 will alternately close and open the bypass valve 6, depending on draft conditions. When the draft exceeds a predetermined limit the valve 6 closes and the small pump will feed pressure fluid into the ram cylinder 19 through lines 33, 66, branch 77 of passage 64, bore 78 of plug 79, radial bores 81, passage 73, chambers 59, 58, passage 71 and line 72. As a result of such pressure fluid delivery from the small capacity pump 2 into the lifting ram cylinder 19 While the implement is advanced in working position, some of the weight of the implement and from the tractor front wheels will be transferred to the tractor rear driving wheels. The additional weight thus imposed upon the tractor drive wheels will improve the ability of the tractor to pull a heavy load without wheel slippage.

When the valve 8 is in the weight transfer position as shown in FIG. 3, the small capacity pump 2 is operable to deliver pressure fluid to the lifting ram 3 independently of the large capacity pump 1.

In the lowering position of the valve 9 as shown in FIG. 4, the land 89 establishes communication between the first inlet chamber 52 and first outlet chamber 54, and it interrupts communication between the first transfer charnber 59 and the delivery chamber 58. The land 91 is 1neffective. The land 92 disconnects the second inlet chamber 53 from the second transfer chamber 61, and the land 93 establishes communication between the delivery chamber 58 and the second exhaust chamber 56. Pressure fluid may return rapidly from the ram cylinder 19 to sump through line 72, passage 71, chambers 58, 56, exhaust line 68 and sump line 10. The large capacity pump 1 feeds back to sump through chambers 52, 54, exhaust line 67 and sump line 10, unless called upon to perform other functions. The small capacity pump 2 will feed back to sump through line 33, open valve 6 and exhaust line 36, assuming that the tractor is standing still and no draft is transmitted through the draft sensing device 4.

A centering and detent mechanism 96 is operatively associated with the valve spool 84, for controlling manual adjustment of the valve by means of the lever 86.

In general terms, the hydraulic ram of the power lift mechanism 3 represents a hydraulic fluid motor which has a driven element 17 movable to' implement raised and implement lowered positions. The valves 6 and 9 together with their associated connecting linesrepresent fluid distributing means which are operable to convey pressure fluid from a first pump 1 to the fluid motor and thereby move the driven element of the latter from an implement lowered to an implement raised position, independently of fluid delivery from a second pump 2, as illustrated by FIG. 2; and to convey pressure fluid from the second pump to the fluid motor and thereby bias the driven element of the fluid motor toward its implement raised position independently of fluid delivery from the first pump as illustrated by FIG. 3. In particular, the fluid distributing means include a bypass valve 6 for the second pump, and motion transmitting means as represented by the lever 41 and cable 43, which are operable to close the bypass valve upon movement of the movable element 17 of the fluid motor to its implement raised position. In addition to the motion transmitting means 41, 43, the herein disclosed power lift and weight transfer system includes a draft sensing device which is operatively connected with the bypass valve 6 so as to close and open the latter in response to draft load increases and decreases, respectively, sensed by said draft sensing device.

It should be understood that it is not intended to limit the invention to the specific systems herein shown and described for purposes of illustration, as various modifications within the scope of the appended claims may occur to persons skilled in the art.

Having now particularly described and ascertained the nature of our said invention and the manner in which it is to be performed, we declare that what we claim is:

1. In a hydraulic power lift system for tractors, an implement adapted to be connected to said tractor and controlled by said lift system, the combination of a first and second fluid pump having large and small output capacities, respectively; a fluid motor operatively connected to said lift system and having a driven element movable to position said implement in raised and lowered positions; a draft sensing device; a bypass valve for said second pump having a movable control element operatively connected with said draft sensing device so as to close and open said bypass valve in response to increase and decrease, respectively, of draft sensed by said draft sensing device; a manually operable control valve connected in fluid communicating relation with said first and second pumps and with said fluid motor, said control valve being selectively adjustable independently of said bypass valve to position said implement in hold, lift, lower and weight transfer positions and, upon adjustment to said weight transfer position being effective in response to closing and opening, respectively, of said bypass valve, to activate and deactivate said fluid motor independently of pressure fluid delivery thereto from said first pump; and motion transmitting means operatively connected with said driven element of said fluid motor and with said control element of said bypass valve so as to close and open said bypass valve in response to movement of said driven element of said fluid motor in implement raising and lowering directions, respectively, beyond a predetermined position .of adjustment.

2. A hydraulic power lift system as set forth in claim 1 wherein said predetermined position of said driven element of said fluid motor is disposed closely adjacent to the maximum implement lift position of said driven element.

3. A hydraulic power lift system as set forth in claim 1 wherein said movable control element of said bypass valve is spring biased toward valve opening position, and wherein said motion transmitting means include a lost motion connection between said driven element of said fluid motor and said control element.

4. In a hydraulic power lift system for tractors having a rockable implement lift structure and an associated hydraulic actuating ram, an implement adapted to be operatively connected to said actuating ram for actuation "7 thereby, the combination of a first and second fluid pump having large and small output capacities, respectively; a bypass valve for, said second pump; a draft sensing device operatively connected with said bypass valve so as to close and open the latter in response to increase and decrease, respectively, of draft sensed by said draft sensing device; a pivoted actuating element for said bypass valve; one way motion transmitting means operatively interposed between said lift structure and actuating element so as to close and open said bypass valve in response to movement of said implement when raised and lowered, respectively, beyond a predetermined limit position; and a manually operable control valve connected in fluid communicating relation with said first pump, second pump and ram, said control valve being selectively adjustable independently of said bypass valve to position said implement in hold, lift, lower and weight transfer positions and, upon adjustment to said weight transfer position being eifective in response to closing 8, and opening, respectively, of said bypass valve by said draft sensing device, to activate and deactivate said ram independently of pressure fluid delivery thereto from said first pump.

References, Cited by the Examiner UNITED sTATEs PATENTS 1,932,761 10/33 West 60--52 2,192,778 3/40 Stacy 60-97 2,659,204 11/53 Conway et -al. 60-52 2,964,113 12/60 Presnell et a1 l729 2,964,908 12/60 Pomper et a1. 6052 2,998,851 9/61 Marind-in 172-10 X 3,003,568 10/61 Merritt et a1. l729 3,014,536 12/61 Marindin et a1 l723 X 3,064,426 11/62 Furia et a1. 60-52 ABRAHAM G. STONE, Primary Examiner. 

1. IN A HYDRAULIC POWER LIFT SYSTEM FOR TRACTORS, AN IMPLEMENT ADAPTED TO BE CONNECTED TO SAID TRACTOR AND CONTROLLED BY SAID LIFT SYSTEM, THE COMBINATION OF A FIRST AND SECOND FLUID PUMP HAVING LARGE AND SMALL OUTPUT CAPACITIES, RESPECTIVELY; A FLUID MOTOR OPERATIVELY CONNECTED TO SAID LIFT SYSTEM AND HAVING A DRIVEN ELEMENT MOVABLE TO POSITION AND IMPLEMENT IN RAISED AND LOWERED POSITIONS; A DRAFT SENSING DEVICE; A BYPASS VALVE FOR SAID SECOND PUMP HAVING A MOVABLE CONTROL ELEMENT OPERATIVELY CONNECTED WITH SAID DRAFT SENSING DEVICE SO AS TO CLOSE AND OPEN SAID BYPASS VALVE IN RESPONSE INCREASE AND DECREASE, RESPECTIVELY, OF DRAFT SENSED BY SAID DRAFT SENSING DEVICE; A MANUALLY OPERABLE CONTROL VALVE CONNECTED IN FLUID COMMUNICATING RELATION WITH SAID FIRST AND SECOND PUMPS AND WITH SAID FLUID MOTOR, SAID CONTROL VALVE BEING SELECTIVELY ADJUSTABLE INDEPENDENTLY OF SAID BYPASS VALVE TO POSITION SAID IMPLEMENT IN HOLD, LIFT, LOWER AND WEIGHT TRANSFER POSITIONS AND, UPON ADJUSTMENT TO SAID WEIGHT TRANSFER POSITION BEING EFFECTIVE IN RESPONSE TO CLOSING AND OPENING, RESPECTIVELY, OF SAID BYPASS VALVE, TO ACTIVATE AND DEACTIVATE SAID FLUID MOTOR INDEPENDENTLY OF PRESSURE FLUID DELIVERY THERETO FROM SAID FIRST PUMP; AND MOTION TRANSMITTING MEANS OPERATIVELY CONNECTED WITH SAID DRIVEN ELEMENT OF SAID FLUID MOTOR AND WITH SAID CONTROL ELEMENT OF SAID BYPASS VALVE SO AS TO CLOSE AND OPEN SAID BYPASS VALVE IN RESPONSE TO MOVEMENT OF SAID DRIVEN ELEMENT OF SAID FLUID MOTOR IN IMPLEMENT RAISING AND LOWERING DIRECTION, RESPECTIVELY, BEYOND A PREDETERMINED POSITION OF ADJUSTMENT. 